U.S. Severe Weather Forecast (Coup d'œil sur la convection)

Day Three

acus01 kwns 192003 
Storm Prediction Center ac 192001 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0301 PM CDT sun Apr 19 2015 

Valid 192000z - 201200z 

..there is an enh risk of severe thunderstorms from eastern OK eastward across the 
Ozarks to the lower MS valley region...and southward into northern la and parts 
of East Texas... 

..there is a slight risk of severe thunderstorms from southeastern Kansas/eastern OK/East Texas eastward to 
parts of the Carolinas/GA/N Florida... 

..there is a marginal risk of severe thunderstorms in areas surrounding the slight 
risk area... 

Scattered severe thunderstorms will continue over parts of the 
south-central states mainly this afternoon and evening...with very 
large hail...damaging winds...and a few tornadoes. Severe storms 
may also occur over parts of the southeast through the period with 
damaging gusts...a few tornadoes...and isolated hail possible. 

Aside from minor line adjustments...severe risk areas and reasoning 
issued earlier remain valid this update. Severe storms continue 
moving eastward across Georgia/SC/N Florida at this time...while storm development is now 
underway farther west across southeastern Kansas/OK/E Texas on western fringes of the 
enhanced risk area. Expect convection -- and associated severe risk 
-- to continue increasing across this area over the next few of 

.Goss.. 04/19/2015 

Previous discussion... /issued 1129 am CDT sun Apr 19 2015/ 

A complex forecast scenario is developing for the Southern Plains 
into the southeast states today...with the potential for an active 
severe weather episode across parts of OK/AR/TX/la. 

..OK into AR/TN/KY... 
A slow-moving upper low over Kansas is opening up and becoming more 
progressive today...and will move eastward across the middle MS valley 
tonight. Several weaker shortwave troughs will round the base of 
the trough into the arklatex region eastward into the southeast 
states. Meanwhile...cold temperatures aloft associated with the 
upper system will help destabilize parts of OK/TX/AR and lead to 
scattered afternoon thunderstorms. 

Storms will initially form beneath the main upper low over 
north-central and northeast OK...spreading eastward across Arkansas during 
the afternoon and evening. Forecast soundings show steep middle level 
lapse rates and ample cape...along with favorable deep-layer 
effective shear profiles. This will promote supercell storms 
capable of very large hail and damaging winds. As the storms track 
eastward into central/eastern Arkansas this evening...strengthening low 
level winds may enhance the tornado threat...although storms will 
likely have congealed into a more linear structure by then. 
Activity may remain severe well into the evening/night as it spreads 
into west TN/KY. 

..East Texas into la... 
Thunderstorms are also expected to form along a trailing surface 
boundary over East Texas by late afternoon. These storms will be in a 
favorable environment for rotating updrafts capable of very large 
hail and damaging winds...along with an isolated tornado or two. 
This activity should remain intense for several hours...tracking 
into la and western MS before weakening. 

..al/western Georgia this afternoon... 
Several 12z model solutions continue to suggest that thunderstorms 
will develop over parts of Alabama and track eastward into western Georgia 
this evening. This area was affected by widespread morning 
convection...and residual clouds are significantly limiting 
destabilization. Will maintain slight risk in the area in the event 
that rapid heating can occur...but this scenario is not looking 
likely at this time. 

A broad corridor of thunderstorms currently extends from north Georgia 
into the Florida Panhandle. Several storms in this zone have shown 
rotation in the past several hours...with isolated tornadoes and 
wind damage being reported. This activity will likely maintain at 
least some severe risk for several more hours as it spreads 
east-northeastward into parts of SC. 

Mesoscale Discussion

acus11 kwns 192057 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 192056 

Mesoscale discussion 0381 
National Weather Service Storm Prediction Center Norman OK 
0356 PM CDT sun Apr 19 2015 

Areas affected...northern Florida Peninsula 

Concerning...severe potential...watch possible 

Valid 192056z - 192230z 

Probability of watch issuance...40 percent 

Summary...severe weather potential may increase through 22-00z with 
at least one or two storms now beginning to form across the region. 
It is not yet clear that a watch is needed...but trends will 
continue to be monitored for this possibility. 

Discussion...scattered vigorous thunderstorm development is now well 
underway across the interior northern Florida Peninsula...in advance 
of convective outflow spreading inland off the northeastern Gulf of 
Mexico. Strong surface heating to around 90f of a moist boundary 
layer with dew points near 70f has contributed to moderately large 
cape. This is in the presence of at least modest deep layer shear 
near the subtropical jet axis. A couple of these storms probably 
will intensify further during the next few hours...accompanied by 
the risk for large hail and locally strong wind gusts. An area of 
enhanced sea breeze convergence near Melbourne could become the 
focus for new/intensifying convective development...with backed/ 
south southeasterly surface flow contributing to some risk for a 

.Kerr/Hart.. 04/19/2015 

..please see www.Spc.NOAA.Gov for graphic product... 


Latitude...Lon 28838232 29978167 29858092 28268075 28148162 28838232